1. Field of the Invention
The present invention relates to a device for detecting anomalous rise of temperature of a brake
2. Prior Art
In a prior art braking element composed of a disc brake or a drum brake, a friction member is permitted to slidably contact a rotating member composed of a disc or drum which rotates together with a wheel so as to generate braking force. Accordingly, braking frictional heat is generated by braking operation. When the friction member rises in temperature owing to the braking frictional heat, the so-called fade occurs which reduces the braking force, and vapor-lock occurs in the worst case, which inactivates the braking operation.
Fade is a phenomenon where frictional coefficient is reduced so as to lower the braking force as the friction member made of an organic material rises in temperature. For example, in case of using phenolic resin as a binder, heat resistant characteristic of phenolic resin which is not denatured, namely, temperature at which the weight of the phenolic resin is sharply reduced in the atmosphere owing to thermal decomposition ranges from 300.degree. to 350.degree. C. Accordingly, offensive smell is generated at the temperature ranging from 300.degree. to 350 .degree. C. Vapor-lock is a phenomenon where the brake fluid rises to an anomalous temperature whereby a part of the brake fluid is evaporated to be changed to gas, whereby fluid under pressure is not transmitted. Vapor-lock occurs generally in a state where the friction member rises to the temperature higher than the temperature at which fade occurs in the friction member and which influences upon the brake fluid. Meanwhile, boiling point of the brake fluid when the brake fluid absorbs moisture (wet boiling point) is about 140.degree. C.
Whereupon, the prior art braking element is not provided with an anomalous braking element temperature-rise detector for generating a different (unusual) noise, namely, jar. Accordingly, it is impossible to detect that the friction member rises to an anomalous temperature owing to the braking frictional heat, whereby fade or vapor-lock occurs, which causes a problem to render the vehicle in a dangerous state. According the invention, a detector for slidably contacting the disc, when the friction member is worn out and reduced in thickness to the limit of use thereof, is fixed to a back plate of the pad.